Examples of fuel injection systems are shown in U.S. Pat. No. 4,527,738 issued to Martin on Jul. 9, 1985, U.S. Pat. No. 4,568,021 issued to Deckerd et al. on Feb. 4, 1986, and U.S. Pat. No. 5,213,083 issued to Glassey on May 25, 1993. During a fuel injection cycle or phase, fuel is forced from a fuel plunger chamber in which the pressure of the fuel is increased, through a channel and to a tip portion of a needle check blocking fuel flow through one or more spray orifices. The pressurized fuel forces the needle check to move towards an unseated position, uncovering the orifices and permitting the flow of fuel therethrough.
It is often desired to minimize the quantity of the fuel introduced into the combustion chamber early in an injection cycle to minimize engine combustion noise and/or emissions of nitrogen oxides (NO.sub.x). Such a reduction in the quantity of fuel delivered during an early portion of an injection cycle is hereinafter referred to as rate shaping of the fuel delivery. There are several known devices available which permit rate shaping of fuel delivery charges. It is desired to provide a compact and simplified rate shaping device that can be packaged within a fuel injector.
The present invention is directed to overcoming one or more of the problems as set forth above.